Friction stir welding method and component part welded by the method

Abstract

Disclosed is a friction stir welding method for welding two members to be welded which differ in physical properties and/or mechanical properties by abutting the two members to each other, inserting a pin portion of a rotary tool having the pin portion and a shoulder portion to the abutment surfaces of the two members, and moving the rotary tool along the abutment surfaces. The pin portion is inserted to only one of the members, the pin portion is not inserted to the other of the members but only the shoulder portion is set in contact with the other of the members, and, while this condition is maintained, the rotary tool is moved. With this method, only the member on the side where the pin is inserted can be made to undergo plastic flow attendant on a friction stir action. The metal in plastic flow is pressed against the opposite member at an elevated temperature and high pressure, whereby diffusion of atoms is caused in the vicinity of the abutment surfaces, and the members are welded.

What is claimed is:  
     
       1. A friction stir welding method for abutting and welding two members to be welded which differ in physical properties and/or mechanical properties by a friction stir welding technique by use of a rotary tool having a pin portion and a shoulder portion, wherein 
       a welding surface of at least one of said two members is covered with a metal capable of being coupled with both of said members on a metallic basis, said pin portion of said rotary tool is inserted to said members from above the abutment surfaces of said members, wherein said pin portion of said rotary tool is inserted in the state of being biased to the side of the other of said members so that said pin portion is inserted to the coat layer of said metal formed on one of said members but does not reach said one of said members, said shoulder portion of said rotary tool is set in contact with said one of said members on the side where said pin portion is not inserted, and, while this condition is maintained, welding is conducted; and  
       wherein said pin portion of said rotary tool is inserted to the member having a lower melting point, of said two members to be welded.  
     
     
       2. A friction stir welding method as set forth in  claim 1 , wherein one of said members to be welded is iron or an iron alloy, while the other of said members is copper or a copper alloy, the welding surface of said iron or iron alloy is coated with an alloy of silver and copper, and said pin portion of said rotary tool is inserted to said copper or copper alloy, wherein said pin portion is inserted to said silver-copper alloy coat layer but is not inserted to said iron or iron alloy. 
     
     
       3. A friction stir welding method as set forth in  claim 1 , wherein one of said members to be welded is stainless steel, while the other of said members is copper or a copper alloy, the welding surface of said stainless steel is coated with the same material as the other of said members, and said pin portion of said rotary tool is inserted to said copper or copper alloy, wherein said pin portion is inserted to said copper or copper alloy coat layer formed on the side of said stainless steel but is not inserted to said stainless steel. 
     
     
       4. A friction stir welding method as set forth in  claim 1 , wherein one of said members to be welded is iron or an iron alloy, while the other of said members is aluminum or an aluminum alloy, a welding surface of said iron or iron alloy is coated with nickel, and said pin portion of said rotary tool is inserted to said aluminum or aluminum alloy, wherein said pin portion is inserted to said nickel coat layer but is not inserted to said iron or iron alloy. 
     
     
       5. A semiconductor apparatus comprising: 
       a heat sink; and  
       a semiconductor device on said heat sink; and  
       wherein said heat sink is composed of a friction stir welded component part which is welded by a friction stir welding method for welding by inserting a pin portion of a rotary tool having said pin portion and a shoulder portion to abutment surfaces of two members to be welded which differ in physical properties and/or mechanical properties, and moving said rotary tool along said abutment surfaces, and wherein said pin portion is inserted only to one of said members, said pin portion is not inserted to the other of said members, only said shoulder portion is set in contact with the other of said members, and, while this condition is maintained, said rotary tool is moved, and wherein a trace of plastic flow attendant on a friction stir phenomenon is seen in the vicinity of the weld portion of one of said members, and a reaction layer due to diffusion of atoms is seen at the weld portion of both of said members.